Relationship between the Concentration of Supplemental Oxygen and Signal Intensity of CSF Depicted by Fluid-Attenuated Inversion Recovery Imaging

Abstract

BACKGROUND AND PURPOSE: Prior reports have described increased signal intensity (SI) of CSF on fluid-attenuated inversion recovery (FLAIR) images of anesthetized patients receiving 100% O₂. This appearance can simulate that of diseases. We evaluated the relationship between the concentration of inhaled O₂ and the development of increased SI of CSF on FLAIR images.

METHODS: FLAIR was performed in 25 healthy volunteers breathing room air and 100% O₂ through a face mask for 5, 10, and 15 minutes. MR imaging, including FLAIR imaging, was performed in 52 patients with no potential meningeal abnormalities under general anesthesia: 21 received an equal mixture of N₂O and O₂, and 31 received 100% O₂. The SI of CSF in volunteers and patients was graded in several locations by using a three-point scale.

RESULTS: SI of CSF significantly increased (P < .05) in various locations, in both volunteers and patients breathing 100% O₂, when compared with SI in the same volunteers breathing room air. Hyperintensity of CSF was not significantly different in volunteers receiving 100% O₂ through a face mask compared with anesthetized patients receiving 100% O₂ through a laryngeal airway or an endotracheal tube. No significant increase in SI occurred in patients receiving 50% O₂, when compared with the SI of volunteers breathing room air.

CONCLUSION: Supplemental oxygen at 100% is a main cause of artifactual CSF hyperintensity on FLAIR images, regardless of the anesthetic drug used. This artifact does not develop when 50% O₂ is administered.